Flow-increasing attachment for culverts



Oct. 4,1927. F A NAGLER FLOW INCREASING ATTACHMENT FOR CULVERTS FiledMarch 24, 1925 INVENTOR.

ATTORNEY.

were a. 4, 1921.

. PAT E NT orrlcs.

FLOYD .A. NAGLER, or am CITY, IOWA. I

rnow-ruonnasme arraonmnnr ron ounvnnrs.

Application filed. March 24, 1923. Serial No. 627,284.

My invention relates to improvements in flow increasing attachments forculverts.

The object of my invention is to utilize the kinetic energy of the waterflowing through '5 the culvert to increase the rate of flow there-- ininstead ofpermitting such ener to be wasted or allowing it tobeqdestructlvely exerted upon the banks of the stream at the outlet.

More specifically stated, it is the object of my invention to providemeans whereby the flow of water through a culvert may be automaticallyaccelerated when the culvert is filled with water, whereby the capacityof the culvert under a given surface elevation of water at theinlet endmay be materially increased as compared with that of ordinary culvertsof the same diameter.

My invention is based upon the discovery so that by providing a culvertwith an extension which will be submerged when the culvert is filled andwhich progressively increases in cross sectional area in the directionof the outlet, it is possible to utilize the kinetic energy of waterpassing through the culvert to'maintain a velocity in the progressivelyenlarging extension sufiicient to not only reduce the resistance at theiunction of the extension with the culvert, 80 ut to actuallydevelop atendency toward a vacuum at that point, whereby the rate of flow throughthe culvert may be accelerated, notwithstanding a reduction in thevelocity of the water at the outlet end of the attachment.

I have further discovered thatthe results possible to obtain by myinvention are not only dependent upon an installation which ensures thesubmergence of the outlet during eriods when the culvert is filledwith-water, ut that the best results are also dependent upon the rate ofdivergence of the walls of the attachment, the best .efiiciencies underordinary conditions being shown where the opposing walls divergesubstantially at the rate of one to ten, i. e., one foot for every tenfeet in length as measured along the axis. A less divergence requiresanincreased length of the attachment and a greater divergence willordinarily be found to reduce the efliciency by absorbing a portion ofthe "energy." Tests of my improvedattachment under actual workingconditions encountered in' the installation of road culverts,havedemonstrated that it is possiblelby the use of myinvention toincrease the capacity of such culverts about fifty per cent.

I am aware of the fact that culverts have been provided with conical orconverging walls at the inlet end and with divergent walls at the outletend designed to prevent erosion of the banks and to prevent thedestructive efi'ects of cross currents and eddies, and in some instancesto reduce the tendency for debris to clog the culvert. But so far as Iam aware no regard has been paid in such instances to the requirementsnecessaryfor increasing the capacity of the culvert, the expandingoutlet ends being previded for substantially the same reason which ledto the use of a contracting inlet, i. e, an inlet having convergingwalls, and without reference to the degree of divergence of the walls atthe outlet, nor to the provision of means for ensuring a submergence ofthe outlet under capacity conditions. 5 Unless these factors are takeninto consideration and the culvert accordingly designed in accordancewith my invention the desired object cannot be attained.

In the drawings z Figure 1 'is a vertical sectional view of a roadwayprovided with a culvert constructed in accordance with my invention.

Figures 2 and 3 are similar views showing modified forms of constructionand arrangement.

Figure 4 is a cross sectional view of my improved attachment orextension member of the culvert, drawn to line 4-4 of Fig. 3.

Like parts are identified by the same reference characters throughoutthe several-views.

In Fig. 1 the culvert proper comprises a series of tile members 1, eachhaving at one end an enlarged portion 2 which serves as an overlamgfannular flange for the next section.

members 3 and 4 at the'outlet end, the outer .shaped at the dischargeend. The degree of e attachment embodyingmy in-v vention comprises thetwo conically tapered expansion in the conical portion is in the ratioof substantially one to ten as above described and at the outlet end thecross sectional area .is more than double that of the cylindricalportion of the culvert, i. e., that of the members 1. Atthe outlet onabutment 6 is provided which is flanked by walls 7 which with the bottomwall 8, are adapted to prevent erosion at the sides of the abutment 6and are also adapted to co-operate with the banks 8 of the stream toensure the retention of sufiicient water at the outlet to keep thesurface level above all portions of the member 4 when the culvert is insuch case,

lled with water, although somewhat below the level of the water at theinlet.

Where the conditions are such that a hori-' zontally outlet end of theattachment submerged under ordinary conditions of capacit flow,

I employlthe construction illustrated m Fig.

2, in w ich'the culvert tube 10 is downwardly inclined in the directionof the outlet, and my improved attachment 11- will, be preferably formedwith its top'portion' substantially a continuation of .walls 14 and abottom wall 15 similar to the tively,

ment areillustrated as composed of corrugated metal, but the characterof the material used is not essential to the invention herein claimed.In caseswhere the culvert is composed of cone te the culvert tube 20 andthe 4 expanding attachment 21 may be formed integrally as a monolithicstructure, (Fig. 'and'may, if desired, be rectangular 1n cross section.The side walls 22 of the extension diverge as clearly shown in Fig. 4and v the bottom wall 23 is also downwardly inclined to a greater'extentthan the top wall 21, the latter being continuous in a straight.

line with the top of the culvert tube or assage 20. The flanking wallsand floor o the abutment extension are similar to those disclosed inFig, 1, the conditions assumed being of the culvert.

such that it is .not necessary to 'provide an inclined floor similar tothe floor 15 in Fig. 2. It will be understood that in formingthese-flanking walls on the abutmentoonsideration should be given, notonly to the prevention of erosion, but also the problem of maintainingthe surface level of the stream at a horizontal plane above the top ofthe expanding attachment or extension member In operation, there is nomaterial difference in the results attained by my improved culvert overthose of an ordinary culvert until the flow' of water becomes sufiicientto fill the culvert and the expandin attachment at the outlet endthereof. ut when the flow is such, as to fill the culvert tube disposedculvert would not have the a sence and raise the level of the water atthe outlet above the expanding attachment,the water tends 'to maintainby inertia the velocity which it has when entering the attachment, andactually maintains a suflicient velocity within the increasing crosssectional areas,

to enable the attachment to carry progressively greater quantities ofwater at the maintained velocity than that which the oul vert tube wouldnormally su ply. Therefore, there is a constant tendency for the waterin the attachment to move away from that which follows it,'and. thiscauses an acceleration of the flow in the smaller cross sectional areas,the effect being that of an increase in head at the inlet end of theculvert. In a glazed tile culvert twenty-four inches indiameter'andtwenty feet long, operating under a normal head of one foot, withadischarging capacity of 23.4'cubic feet or second, I have found that byattachmg my increased to 33.6 cubic feet pen second. A similar test witha culvert thirty inches in diameter and twenty feet long under one foothead of water showed a capacity without my improved attachment of 33.3cubic feet per second and acapacity withthe attachment added of 50.2cubic feet per sec-' ond. The'tests in both cases were made underconditions which were otherwise alike and with the outlet submerged.Similar tests made wi h culverts of varying length and diametersindicate that there .is a variation in the results secured which isdependent upon the length. and diameter of the culvert tube, the lengthof the atimproved extension member the capacity can tachment and theratio of expansion, but

that, in all cases where the above described conditions of installationare observed, a.

very marked increase in the capacity of the culvert is attained by theuse of my invention.

y energy of the water in the culvert is exerted against the body ofwater in the attachment the use of my invention the momentum which isnecessarily movingimore slowly because of the enlarged cross section andwhich, therefore, serves as a water piston to absorb the difference inthe kinetic energy of a given volume of water atthe inlet end of theattachment and that of an volume at the outlet end or point ofdischarge. In absorbing this momentum energyrthe water piston in theattachment ual is somewhat accelerated, but at the outlet, if

the cross sectional area is double'that of'the culvert, the velocitywillbe about one half that of the accelerated culvert water and iconsiderably less than it would be at the out-- let of the culvert ifconstructed in the ordinarv manner. r v

y invention, therefore, serves the double purpose of utilizingthekinetic energy of the water flowing through the culvert to reduce theresistance, thus increasing the effective head, and of proportionatelyreducing the velocity of the water at the point of final delivery toprevent destructive erosion. I claim s j 1. A culvert provided withdivergent walls at its discharge end forming a progressively enlargingwater passage and p0 sitioned for complete subm'ergence of such passagebelow the level of the stream of water when the culvert is. filled.

2. The combination with the walls of a culvert, of an extension memberat the outlet end thereof, of progressively increasing capacity in thedirection of the outlet, said extension member being disposed for acom-' plete submerslon of 1ts water-carrying portion beneath the levelof thest-ream at the outlet when the culvert is filled.

3. A culvert having a main portion of "substantially equal capacitythroughout, and

a submerged outlet portion, which progressively increases in crosssectional area in the direction of the point of discharge in such aratio as to provide an expanding water piston capable of substantiallyabsorbing the FLOYD ,A. NAGL'ER;

